Add hello

app/controllers/application_controller.rb

 class ApplicationController < ActionController::Base
 class ApplicationController < ActionController::Base
   protect_from_forgery with: :exception
   protect_from_forgery with: :exception
+   def hello
+      render html: "hello,world!"
+   end
 end
 end

config/routes.rb

 Rails.application.routes.draw do
 Rails.application.routes.draw do
   # For details on the DSL available within this file, see http://guides.rubyonrails.org/routing.html
   # For details on the DSL available within this file, see http://guides.rubyonrails.org/routing.html
+
+  root 'application#hello'
 end
 end